[PATCH v5 1/4] gpio: mvebu: improve pwm period calculation accuracy
From: Baruch Siach <baruch@tkos.co.il>
Date: 2021-01-20 16:19:46
Also in:
linux-arm-kernel, linux-pwm
Subsystem:
gpio subsystem, the rest · Maintainers:
Linus Walleij, Bartosz Golaszewski, Linus Torvalds
Change 'off' register value calculation from $off = (period - duty_cycle) * clkrate / NSEC_PER_SEC to $off = (period * clkrate / NSEC_PER_SEC) - $on That is, divide the full period value to reduce rounding error. Reported-by: Uwe Kleine-König <redacted> Reviewed-by: Uwe Kleine-König <redacted> Reviewed-by: Linus Walleij <redacted> Signed-off-by: Baruch Siach <baruch@tkos.co.il> --- drivers/gpio/gpio-mvebu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpio/gpio-mvebu.c b/drivers/gpio/gpio-mvebu.c
index a912a8fed197..c424d88e9e2b 100644
--- a/drivers/gpio/gpio-mvebu.c
+++ b/drivers/gpio/gpio-mvebu.c@@ -715,9 +715,9 @@ static int mvebu_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, else on = 1; - val = (unsigned long long) mvpwm->clk_rate * - (state->period - state->duty_cycle); + val = (unsigned long long) mvpwm->clk_rate * state->period; do_div(val, NSEC_PER_SEC); + val -= on; if (val > UINT_MAX) return -EINVAL; if (val)
--
2.29.2